Ratchet drive for speedometers



RATCHET, DRIVE FOR SPEEDOMETERS Filed May 12, 1928 f (1Q 14 O 11 3. I6

' "ll 9/ G 7 "'7' Patented Mar. 31, 1931 UNITED STATES PATENT. OFFICE HARRY A. TITTENSOR, OF FLINT, MICHIGAN, ASSIGNOR TO A Q SPARK PLUG- COMPANY, OF FLINT, MICHIGAN, A COMPANY OF MICHIGAN RATCHET DRIVE FOR srnnnomnrnns Application filed May 12, 1928. Serial No. 277,337.

This invention relates to measuring instruments and has been designed particularly as an improvement in a ratchet drive for the odometer part of a combined odometer and speedometer as used on motor vehicles.

An object of the invention is to provide an improvementin the ratchet drive for such an instrument. Another object is to provide a simple and economical retaining means for the drive pawl associated with the ratchet wheel. Other objects and advantages will be appreciated from a reading of the following description.

In the drawing accompanying the description:

Figure 1 is a side elevation of aspeedometer frame, parts being broken away to show the improved ratchet drive.

Figure 2 is an elevation facing the rear of the instrument, parts broken away.

Figure 3 is a perspective view of the retainer for the pawl.

Referring by reference characters to the drawing, numeral 9 represents a supporting frame, which frame is to carry the parts of both the speedometer and the odometer. The frame is to be housed within a casing, the casing to be secured as usual to the instrument board of the vehicle. The frame is preferably formed by die-casting. At the upper side is shown a magnet 1 of U-shape. This magnet is to surround the usual speed cup and rotor, these parts not being a part of the invention and not illustrated. As in prior constructions, the frame is formed with a vertical part 2 which is apertured to journal a rotor shaft, the extreme lower end of which is shown at 3 in Figure 2. This rotor shaft is driven by a flexible shaft, also shown in Figure 2, and designated by numeral 4. The die-cast frame has a bore at right angles to the rotor shaft bore in which is journalled a second worm shaft 10, the purpose of this shaft being to operate the odometer mechanism.

The mechanism of the speedometer and odometer need not be further described. It may be mentioned that numeral 5 represents a strap of non-magnetic material which is fastened to the frame as at 6 and which is used to clamp the magnet in position on the frame.

The invention with which this application is concerned relates to thedriving means by which the shaft 10 drives the ratchet wheel 13, which is to rotate the odometer wheels.

At 11 is an eccentric pin projecting from one end of shaft 10. Upon this pin is located the apertured end of a reciprocating pawl 12, the purpose of the latter being to actuate the ratchet wheel 13. Associated with the ratchet wheel 13 will be employed gearing elements to drive both the conventional sets of odometer wheels, the wheels of the season set and the wheels of the trip set.

The pawl projects through an opening 7 in the frame member and engages the teeth of Wheel 13, as shown in Figure 1. Owing to the eccentric position of the pin 11 on shaft 10, the pawl has a reciprocating movement in twodirections. It reciprocates to the left in Figure 1 and rotates the ratchet wheel 13. Thereafter, it reciprocates to the right, in which movement it is inoperative to rotate the ratchet wheel. Friction means may be employed, if desired, to prevent any reverse movement of ratchet wheel 13. No such means is illustrated as this is not a part of the invention.

To retain the pawl on the pin there is used an Lip-turned portion 14 of a retaining member designated as a whole by numeral 15. This member is secured to an outwardly directed car 16, which is an integral part of the die-cast frame by means of a rivet or an equivalent fastening means. Projecting in a direction parallel with the pawl and engaging its underside is a leg 17 forming an integral part of the member 15, which leg is to act resiliently upon the pawl and urge it into engagement with the teeth of the ratchet wheel. j i

Positioned above the pawl and adapted to engage its upper surface is a pin 18 project ing from theside of frame 9. As the shaft'i i rotates, the eccentric pin on the end of shaft 10 gives the pawl. a reciprocating movement to the left and thereby rotates the ratchet wheel 13, the resilient end 17 of member 15holding the pawl, in engagement Withi the ratchet wheel. In its retrograde movement, a movement to the right in Figure 1, the spring 17 would still tend to hold the pawl against the ratchet wheel and the tooth of the pawl would slide over the teeth of the ratchet and produce a clicking noise. To avoid this noise, the upper face of the pawl is so shaped that in the retrograde movement of the pawl, the pin 18 engages the upper surface and pushes the pawl away from the ratchet wheel against the tension of spring members 17. By this means, any unnecessary wear between the pawl and ratchet is avoided and the clicking noise above referred to does not occur.

By the above arrangement, a ratchet drive is rendered available which is cheap to manufacture and which avoids the use of several gears between the second worm gear and the odometer wheels. Such a drive does not require the refinement in dimensions of parts and the use of the pin 18 with such a pawl avoids undue wear and noise.

The part 15 is a very economically made device to yieldingly hold the pawl on its eccentric driving pin 11.

I'claim:

1. In combination, a rotatable ratchet wheel, a reciprocating pawl, yielding means to pass said pawl toward said ratchet wheel, and a pin engaging said pawl when moved in its inoperative direction to lift said pawl from the ratchet wheel against the action of said spring, said yielding means having an angular part engaging the side of said pawl and holding said pawl from movement transversely of its direction of reciprocation.

2. A pawl retaining clip having at one end faces angularly related, one face adapted to engage and hold a pawl in position, the other to receive fastening means, the other end of said clip engaging and resiliently holding the pawl in operative position relative to the ratchet it is to engage.

3. In combination, an instrument frame, a ratchet wheel rotatably carried thereby, a driven shaft having an eccentric pin, a pawl pivoted on said pin and reciprocated by the rotation of the driven shaft, said pawl engaging said ratchet wheel to rotate the same in one direction of reciprocation, a pin located adjacent said pawl, said pawl shaped to engage said pin and be lifted by the pin from engagement with the ratchet wheel when reciprocated in the opposite direction, said frame having an ear, and means secured to said ear, said means including a resili'ent element engaging said pawl and urging it toward said ratchet wheel, said means also having a. part thereof engaging said pawl and holding it on said eccentric pin.

4. In combination, a frame, a rotatably mounted ratchet wheel, a reciprocating pawl, a shaft journaled in said frame and having HARRY A. TITTENDSQR. 

